Paramyxoviruses are enveloped, negative-sense single-stranded RNA viruses that are divided into two subfamilies, Paramyxovirinae and Pneumovirinae. Viruses in the subfamily Paramyxovirinae have been associated with a number of emerging diseases in humans and various animals in the past two decades (1-9). There are currently five genera within the subfamily Paramyxovirinae, namely Respirovirus, Rubulavirus, Morbillivirus, Henipavirus and Avulavirus, although some members of the subfamily remain unclassified. Among members of Paramyxovirinae, measles virus, mumps virus, and human parainfluenza viruses 1 to 4 are most well known human paramyxoviruses which cause outbreaks of respiratory to systemic infections (10-12). Three novel rubulaviruses, Tuhoko virus 1, 2 and 3, from fruit bats in mainland China and a novel unclassified paramyxovirus, Tailam virus, from Sikkim rats in Hong Kong were recently reported (13,14). Despite the presence of paramyxoviruses in a variety of animals, no paramyxoviruses have been naturally observed in cats, although there is controversial evidence that cats may be infected with parainfluenza 5 virus (15,16).
Cats and dogs are the most common domestic animals and pets worldwide. As a result of their close relatedness, interspecies jumping of viruses among these two kinds of animals is not uncommon. For coronaviruses, feline coronavirus and canine coronavirus are classified under the same species Alphacoronavirus 1, and feline coronavirus type II strains were generated by double homologous recombination between feline coronavirus type I strains and canine coronavirus (17). For parvoviruses, the fatal canine parvovirus that emerged in the 1970s also originated from a feline parvovirus, feline panleukopaenia virus (18,19). As for herpesviruses, canid herpesvirus 1 and felid herpesvirus 1 are closely related and are classified under the genus Varicellovirus (20). Furthermore, for papillomaviruses, canine oral papillomavirus and feline papillomavirus are also closely related and are classified under the genus Lambdapapillomavirus (21). Dogs are well-known hosts of a paramyxovirus, canine distemper virus, in the genus Morbillivirus (22), but no paramyxoviruses have ever been discovered in domestic cats.
Many feline diseases have no known causes. For example, the cause of most cases of feline tubulointerstitial nephritis is hitherto unknown and therefore treatment is mainly supportive and prevention is difficult. Tubulointerstitial nephritis (“TIN”) involves primary injury to renal tubules and interstitium and is the most common cause of renal failure and one of the leading causes of deaths in cats. However, the cause of most cases of feline TIN remains unknown and therefore treatment is mainly supportive and prevention is difficult. With millions of cats in households around the world, the disease burden from TIN is great. For example, in the United States of America, it is estimated that there are 75 million household cats, while there are an estimated 8 million household cats in United Kingdom (data from Chomel B B, Sun B., Zoo noses in the bedroom. Emerg Infect Dis. 2011 February:17(2):167-72.). The capability to diagnose, treat or prevent feline kidney or other diseases would have a great benefit.
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